Neuro230 Exam 1

dendrite

Specialized mechanisms for receiving information (receiving antennae for other neurons)

soma

Cell body of the nucleus that integrates incoming signals

axon hillock

Location of action potential generation

vesicles

Located inside synaptic bouton; contain neurotransmitter molecules that the neuron can release

astrocytes and microglial cells

• surround blood vessels in brain to create blood-brain barrier

• neurochemical modulation

• modulate neurotransmission signals

• take care of metabolic wastes (ex. forming scar tissue)

stroke occurrence

1. blood vessel bursts, pressure of leaking blood can kill neurons

2. obstructed blood vessel that cannot transport nutrients to neurons, which can kill neurons

oligodendrocytes

provide electrical insulation

resting potential (RP) of neuron

negative on inside due to more negative ions

inclusive fitness

• aggregate fitness of a gene; total fitness accumulated across all copies that gene compared to the fitness of other competing genes in the population

• a trait which benefits gene copies wherever they are could be selected even if that trait led a loss for the individual who’s carrying the gene

precocial

offspring that are born or hatched in an advanced state and are able to feed and move independently shortly after birth

altricial

species born or hatched in an undeveloped state that require extensive care from parents or caregivers to survive and grow

intersexual selection

(aka mate choice) the process in which individuals of one sex choose their mates based on specific traits or characteristics

• driven by the preferences of the opposite sex, where individuals with desirable traits are more likely to be chosen as mates

• can lead to the evolution of elaborate displays, behaviors, or physical attributes in certain species, as individuals compete to attract mates

• plays a crucial role in shaping the evolution of reproductive strategies and the development of secondary sexual characteristics

intrasexual selection

members of one sex compete with each other for access to mates of the opposite sex

intrasexual vs. intersexual selection

Intrasexual selection: Competition among individuals of the same sex for access to mates. It often involves direct combat or displays to outcompete rivals.

Intersexual selection: Selection based on mate choice, where individuals of one sex choose mates based on certain desirable traits or characteristics. It can lead to the evolution of elaborate displays or behaviors to attract mates.

polygyny

mating system where a male individual forms exclusive relationships with multiple female individuals

polyandry

mating system where one female individual has multiple male mates

parental investment

allocation of time, energy, and resources by parents to ensure the survival and reproductive success of their offspring. It includes activities such as providing food, protection, and care, and can vary greatly among different species

cistron vs. exon vs. gene

Cistron: A segment of DNA that codes for a single polypeptide or protein

Exon: A segment of DNA that is transcribed into mRNA and is involved in protein synthesis

Gene: A functional unit of heredity, consisting of a specific sequence of DNA that codes for a specific protein or RNA molecule

allele

A variant form of a gene that occupies a specific position on a chromosome. Alleles can differ in their DNA sequence and can determine different traits or characteristics in an organism

homozygous

two identical alleles for a particular gene

What is the relationship between an allele and a gene?

• Allele - Alternative forms of a gene that occupy the same position (locus) on homologous chromosomes.

• Gene - A segment of DNA that codes for a specific trait or protein.

• Relationship - Alleles are different versions of the same gene, providing genetic diversity within a population.

heterozygous

two different alleles for a particular gene

path from a gene to a protein

genetic information encoded in a gene is converted into a functional protein molecule through two main steps: transcription and translation.

1. Transcription occurs in the nucleus and involves the synthesis of an mRNA molecule using DNA as a template.

2. Translation takes place in the cytoplasm and involves the assembly of amino acids into a protein chain based on the instructions provided by the mRNA molecule.

monogenic traits

Traits controlled by a single gene. They exhibit clear patterns of inheritance. Examples include albinism and cystic fibrosis.

PKU disease

(Phenylketonuria) a genetic disorder that affects the body's ability to break down an amino acid called phenylalanine due to lack of enzyme phenylalanine hydroxylase converting it into tyrosine.

• recessive allele present on both chromosome 12s

• buildup of phenylalanine in the blood, which can cause intellectual disabilities, developmental delays, and other health problem

• treatment involves following a strict low-phenylalanine diet

gene-brain-behavior relations

• epigenetic interactions

• “indirect” coding

• flexibility to genetic coding

gene knock out vs. knock down

monogenic changes

• out: knock out a particular gene so it doesn’t code its protein

• down: weaken coding of one gene’s protein

Chimeric mice

a “mutant” mouse named after the mythological Chimera (composed of multiple animal species) that has undergone gene manipulation

• insert new cistron/gene containing exons that code a new protein: new DNA

• stem cell injected into embryo during blastula stage

• mutant mouse made up of new gene cells and its original cells

polygenic traits

traits controlled by many different genes

epigenetic interaction

genes interacting with environment (physical and chemical)

• indirect coding

• sensory stimulation and neural activity: ex) maternal licking for mice pups positively impacts neural development

gene identity

gene exists simultaneously in multiple locations so identity = pattern of DNA molecules

kin selection for altruism

if the gain to the recipients divided by the cost to the altruist is greater than 1/r, then the trait will be selected

r (relatedness)

• relatedness beyond what is commonly shared in the population beyond the 99.5% among all humans or beyond the 85% between us and mice

• 85% of genes shared with mouse, but chromosomes look different

• sum of ½ raised to the power of # of genetic links ; ex) mother to you or sibling to you = ½, grandparent to you = ¼, cousin to you = 1/8

requirements for pure altruism (selected by selfish gene strategies)

• low kin dispersal: family members tend to stick around and be near each other

• live in very small family groups (need to differentiate kin from non-kin)

• belding squirrel example: only females give alarm calls, and the caller is kin

selfish gene and psychology

gene pressures do not replace psych; do not create individuals who have to calculate inclusive fitness → gene pressures shape emotional responses

ex) squirrel pup swap: pup helps “family”, who is not genetically family but is the group they grew up in

altricial vs. precocial determinant

precocial species make lots of gene copies because they do not have to provide much parental care

• altricial species prioritize taking care of offspring (selfish gene strategy)

major stockholder pressure

relative investment made by each parent; whichever sex makes larger investment will likely give most parental care; minor investment can more easily abandon offspring

hot potato pressure

if parents are not simultaneously together making the offspring (sequential manner), whoever is left last with offspring has greatest pressure to stay

intersexual selection pressure

between two sexes, can play out toward polygamy or monogamy

• less investment parent may have many other mates

potential parent-offspring conflict

conflict of genetic self-interest between offspring and potential second offspring

changing genetic makeup of cistron

changes the protein that develops that is translated from that gene

to maintain electrochemical gradient, the Na/K pump transports OUT __ sodium ions for every __ potassium ions it brings in, and thus hyperpolarizes the resting potential

3, 2

traditional dogma (not always true)

DNA nucleotides code the transcription of molecular mRNA codes, that is going to code the translation of a particular protein, which will then be expressed

cistron

tiny bit of a gene that codes a protein, contains exons and introns within it

• exon = part that is actually coding the protein

• intron = tend not to code a full protein (might code for other things like micro-DNA), “interruptors” of exons within a cistron

pleiotropy

when a single gene can change many traits together

hygienic honeybee

shows that the hygiene behavior in honeybees is recessive and monogenic, and that there are TWO monogenic recessive traits, one for gnawing the cell cap off if a dead larvae is scented and the second one is to pick up a dead larvae from an uncapped cell and carry it out of the hive

transgenic gene manipulation

new gene is put into genome; codes a new kind of protein, allows for selectively target NT neurons

optogenetics

target specific neuron type with Cre-lox system: photoreceptors expressed only if neuron contains Cre recombinase enzyme → can selectively target an NT in mice

• virus has Cre-targeted promoter: only upon encountering Cre recombinase does it flip the transcription of the opsin gene to activate it so it makes the photoreceptor molecule

• opsin molecules change shape and open ion gates so neurons can fire

• neuron starts making photoreceptor opsin

• sprouts the photoreceptors on the membrane of the neuron, and if light is shined onto them, they change shape and open ion gates

Huntington’s disease

• caused by monogenic dominant cistron

• Huntington allele found on chromosome 4

• uncontrollable movements, cognitive impairments, death

• over-repeating of gene sequences

lock and key model

lock is synaptic receptor, key is ligand (chemical able to bind to a receptor, like drug or NT)

ions overview

• Na+ (most are outside neuron), Cl- (also outside), K+ (inside)

sodium-potassium pump

• about 1/3 of neuron’s energy is used

• ejects 3 Na+, grabs 2 K+ from outside

• RP=exporting extra + charge outward and making inside negative

• reaching energy threshold changes shape of gate molecule, opening it → sodium (+) can enter the neuron (-), causing rising spike in energy

• gate opens all the way every time

consequences of sodium-potassium pump stopping

• blockage of sodium gates means no action potential → muscles do not receive message to complete actions like breathing

absolute refractory period

sodium gate remains closed after opening, acting as separation for neurotransmission (otherwise, a “backlash wave”/ripples would interfere with later transmission)

Leonardo de Vinci

performed 1st ever neuroanatomy experiment using ox brain and molten wax to figure out ventricles

conclusions for ESS

• gene selection for types of behavior

• gene selection depends on environment

• genes can be selected even if not in species’ best interest

directional selection

• moves a population in a direction with regard to a trait (giraffes getting longer necks to get to top branches)

disruptive or divergent selection

• moves a species in two directions at the same time, even splitting population in two extremes (not adapted to the middle range)

• ex. light vs dark moths but no middle moth

convergent selection

• two different groups both move toward the same direction due to shared selection pressures; “mimic” traits via shared selection pressures

homoplasy/homoplastic

same trait in two different species that is not homologous (not inherited from a common ancestor), caused by convergent evolution

ex. fins are ___ in dolphins vs. fish

homology/homologous

preservation of the same ancestral trait (and genes) in multiple descendant species from the same common ancestor

• five cat toes, five vestigial digits in whales, five human fingers (shared trait)

• forelimbs are ____ in dolphins and us

Aplysia model, Eric Kandel (psychological convergence)

• Kandel figured out the molecular basis of learning and memory of Aplysia (mollusks) → classical Pavlovian conditioning

• Aplysia would be a model for human neuronal learning if conditioning is a homologous trait inherited from ancestors

• would not be if conditioning is homoplastic trait selected by convergent evolution

characteristics that increase AP speed

myelination and a thicker axon diameter

role of cadherin, CAMs, and semaphorin

signaling neuron growth

central dogma flow (three terms)

DNA → mRNA → protein

cFos

gene codes for same-named protein and is a marker of neuron activation

biopsychological perspective

behavior emerges as a psychological trait and the mind is evolved to produce behavior

saltatory jump

AP can jump over insulated parts of the neuron to its target

nodes of Ranvier

a gap in the myelin sheath (unmyelinated) that acts as a recharge checkpoint for AP to keep jumping along axon without losing speed

Golgi vs. Cajal

G thought there was 1 neuron, C thought there were many neurons making connections

neurotransmitter release

AP opens calcium gates, calcium ions mostly outside of neuron, causes vesicles to mind to membrane and release NT into cleft

ionic/ionotropic receptor

• opens ion gates directly

• causes post-synaptic potential

metabolic/metabotropic receptor

turns on messenger signal systems so that second signals (or further) do the work (opening gate, change transcription, etc.)

neural receptor

protein molecule embedded in the neural membrane; chemical “lock”

excitatory post-synaptic potential (EPSP)

depolarization of postsynaptic membrane due to inflow of positive ions, increase likelihood of PS AP

inhibitory post-synaptic potential (IPSP)

hyperpolarization of postsynaptic membrane, decrease likelihood of AP

ionic vs. metabolic

I: faster latency, shorter duration

M: slower latency, longer duration

how cocaine affects brain

actively blocks dopamine transporter (preventing re-uptake), leaving a surplus of dopamine in the synapse

summation

• sum of several potentials can be large enough to reach threshold and generate AP

• addition of impulses at the axon hillock; strength increased by summation of several inputs

• temporal summation: integrating successive inputs, building on top of the last in a successive fashion (firing multiple times, relevant to strength or intensity)

• spatial summation: several simultaneously-generated potentials at different synapses add up

autoreceptor

typically inhibitory on presynaptic neuron, measures own NT release, negative feedback signal and regulatory device, highly sensitive

alleles and stress resistance

long allele for serotonin transporter = better resistance to stress